1. Field of the Invention
The present invention relates to a cosmetic composition for skin whitening and, more particularly, to a cosmetic composition for skin whitening that contains at least two selected from the group consisting of a Magnolia obovata bark extract, a Citrus unshiu peel extract, a wild soybean extract, a Ginkgo biloba leaf extract, and a Honeysuckle extract, to improve or prevent skin pigmentation and dark-toned skin and substantially inhibit a production of melamine, thereby providing a whitening effect.
2. Background Art
Human skin color (complexion) and pigmentation such as formation of melasma or skin spots are ascribed to various factors, including the activity of melanin-producing melanocytes, the blood vessel distribution, the skin thickness, and the existence of body pigments such as carotenoids, bilirubin, etc. Among these factors, the primary determinant is a darkening pigment called “melanin”, which is produced by the actions of different enzymes in melanocytes. There are three main factors that affect melanin production: genetic factors, physiological factors related to hormone secretion, and environmental factors such as stress, ultraviolet (UV) irradiation, etc.
Melanins that determine the skin complex are produced in melanocytes, where different enzymes such as tyrosinase participate together in polymerization oxidation reaction using amino acid called “tyrosine” existing in the body as a substrate to produce dark brown pigments, melanins. The melanins thus produced migrate towards the epidermal cells called “keratinocytes” along melanocyte dendrites and form a hat-shaped structure around the nuclei in the keratinocytes to play an important role of protecting DNAs from UVR-induced damage and eliminating free radicals, thereby protecting proteins in the cell. There exists no enzyme for decomposition of melanins. Instead, melanins are removed along with dead keratinocytes shed from the skin. An over-production of melanin results in hyper-pigmentation that shows up as melasma, freckles, spots, etc. with an adverse effect in the cosmetic aspect. Such a UVR-induced hyper-pigmentation has become more serious with an increase in the population enjoying the leisure time with outdoor activities and hence posed heavy psychological burdens in the skin cosmetic aspect to prevent a normal social life in the worse cases. For example, Asian women have taken a liking to a fair skin and considered a fair skin as the criteria for beauty, so there has been an increasing desire for prevention and improvement of pigmentary disorders or hyper-pigmentation. Hence, with an increasing need for developing whitening products to prevent an over-production of melanin, many attempts have been made to contrive whitening products, such as, for example, tyrosinase inhibitors (e.g., kojic acid, arbutin, etc), hydroquinone, vitamin A, vitamin C as a representative antioxidant, and their derivatives. These whitening products are, however, limited in their uses due to some problems in regard to skin safety, stability in formulation, and insufficient whitening effect. The conventional whitening products also have much to be desired to meet the latest customers' desires for a fundamental whitening effect, since they because their whitening effect is only temporary and cannot guarantee the skin health in many aspects.
It has been recently reveled that the simple whitening techniques in association with inhibition of melanin production and promotion of melanin secretion cannot offer a fundamental achievement of the whitening effect. As the development of biotechnology discloses that skin pigmentation involves a considerably complicated mechanism, especially noteworthy are bio-scientific whitening researches for imposing a whitening effect on different target paths simultaneously to achieve a more fundamental whitening effect. There have also been arguments that whitening cosmetic products have a stronger whitening effect when applied on several targets rather than on one or two targets. With recent reports that whitening is closely related to ageing, it is getting more persuasive to treat the pigment-related skin problems, such as skin complexion, melasma, or spots, depending on the healthy condition in the skin. Accordingly, studies have been actively made on the approaches for analyzing and managing the microscopic environment surrounding melanocytes to fundamentally improve the problem with the pigmented skin area which is hard to remove of over-produced melanin.
There is little difference in the number of melanocytes in the skin among races, but a considerably greater number of melanins are produced in the skin of black people upon exposure to UV radiation. In other words, the skin color depends on the produced amount of melanins in the melanocytes. In regard to this, a precise analysis on the melanocytes and their microscopic environment has revealed that the production of melanins have a close relation to the five factors: sensitivity of melanocytes, DNA denaturation of melanocytes, stimulation of inflammation substances on melanocytes, melasma blood vessels around melanocytes, and melanocyte-supporting DEJ (Dermal-Epidermal Junction) collagen fibers. With a problem related to the five factors, the skin sensitively responds to the stimulation from the external harmful environment to produce more melanins, which then migrate downwards in a part of the skin and become difficult to remove from the skin.
The problem with the five factors includes, for example, over-production of melanin in melanocytes under weak stimulation; increase of stimulus induced by inflammation; readiness of DNA denaturation of melanocytes; readiness of production of melasma blood vessels; or deteriorated elasticity of melanocyte-supporting DEJ. Such an unhealthy condition of melanocytes and their environments causes over-production of melanins under weak stimulation, making melanins difficult to remove from the skin and resulting in pigment-related skin problems such as skin spots and dark-toned skin. There is hence a pressing demand for studies on an approach to fundamentally make the ecosystem of the melanins in the skin healthy.